Executive Summary

Conventional methods for specifying data centre density are ambiguous and misleading. Describing data centere density using Watts/ft2 or Watts/m2 is not sufficient to determine power or cooling compatibility with high density computing loads like blade servers. Historically there is no clear standard way of specifying data centres to achieve predictable behavior with high density loads. An appropriate specification for data centre density should assure compatibility with anticipated high density loads, provide unambiguous instruction for design and installation of power and cooling equipment, prevent oversizing, and maximise electrical efficiency. This paper describes the science and practical application of an improved method for the specification of power and cooling infrastructure for data centres.

Introduction

The specification of operating power density for data centres and server rooms is a growing challenge for IT professionals. Specifying data centres at the traditional densities of 40-80 Watts/ft2 (430 - 861 Watts/m2) will result in the inability to reliably deploy the latest generations of IT equipment. Specifying data centres at the 600-1000 Watts/ft2 (6458 – 10764 Watts/m2) operating density of the latest generations of high density IT equipment will result in data centres that stress the limits of data centre power and cooling technology and result in extraordinary capital costs as well as low electrical operating efficiencies.

The density planning problem is further exacerbated by the need to design a data centre to operate through a number of IT refresh cycles where the nature of future IT equipment to be installed is unknown.

The historical method of specifying data centre density in Watts/ft2 provides very little useful guidance for answering critical questions that are faced by data centre operators today. In particular, the historical power density specification does not answer the key question: “What happens when a rack is deployed that exceeds the density specification?” This is a very practical question because the typical data centre today has a density rating of 1.5 kW per rack while typical IT equipment has a greater power density of 3-20 kW per rack.

A new and more complete method of specifying data centre power density is needed. An improved method would address the following needs:

• Assuring compatibility with high density IT equipment

• Avoiding waste of electricity, space, or capital expense

• Providing a means to validate IT deployment plans to the design cooling and power capability